Magnetically-controlled heat treatment of materials



March 2 1926. 1,575,178

D. s. ODONOVAN MAGNETICALLY CONTROLLED HEAT TREATMENT OF MATERIALS Filed Feb. 29, 192 2 Sheets-Sheet 1 March 2 1926. 1,575,178

D. s. ODONOVAN MAGNETICALLY CONTROLLED HEAT TREATMENT OF MATERIALS I Filed Feb. 29, 1924 2 2 Sheets-Sheet 2 6. olDa-riavaz z Patented Mar. 2, 1926.

UNITED STATES 1,575,178 PATENT OFFICE.

DAVID sTAnIsLAUs o'nonovan, or VOGELFONTEIN, TRANSVAAL, SOUTH AFRICA, nssrenoa To ononovan summons LIMITED, or JOHANNESBURG, SOUTH AFRICA.

MAGNETIGALLY-CONTBOLLED HEAT TREATMENT or MATERIALS.

Application filed February To all whom it may concern:

Be it known that DAVID STANISLAUS ODoNovAN, British subject, of 12 Plantation,

Vogelfontein, Transvaal Province, Union of South Africa, residing at 12 Flu ntation, Vogelfontein, Transvaal Province, Union of South Africa, has invented certain new and useful Improvements in Magnetlcally- Controlled Heat Treatment of Materials, of which the following is a specifica-- the drills is minimized as far as tion. v

The present invention has reference to processes and apparatus for heat treating bodies, particularly ferrous bodies, of the kind in which the body is retained in the heating zone by magnetic attraction and 1S withdrawn from the heating zone by an opposing force which is rendered effective by loss of magnetism resulting from the heating.

Whilst this method has hereto been applied to bodies small and light enough to sustained by a magnet, the. present invention enables bodies to be thus treated irrespective of their weight.

The invention further enables the withdrawal to be efiected at any desired temperature within a wide range.

The invention is illustrated in the accom, papying drawings in which-- ing rnace. Fig. II is a transverse section on II, II Fi I. I Iig. III is a plan of the drill supporting and withdrawing mechanism.

Fi IV shows a modification. 2 1s a furnace structure in which is a fire grate 3 or other suitable source of heat, and a flue 4, A mufile 5 extends transverse ly into the flue to be heated by the. hot gases therein. f

The body to be heated (which 1n the 1nstance illustrated is a rock dl'lll tool 6) is mounted on a carrier 7 which is movable either to position the drillin the mufile. as shown or to withdraw it therefrom as indicated by the dotted lines inFig. II. Aweight 8 tends to retract the carrier, whilst a magnet 9 tends to retainthe drill in the muille. As the drill increases in temperature it loses magnetism, and eventually a point.

is reached where the weight overcomes the pull of the magnet and withdraws the earis a front view of a drill hardcn 29, 1924. Serial No. 696,046.

" rier and drill. Such an arrangement is descr1bed in my prior application No 605,927.

A feature of the present invention is that the body is so supported that its weight has no substantial effect on the withdrawng movement. To this end the carrier 7 is pivotally mounted on parallel arms 10 having horizontal movement about vertical axes 11. The effect of varying weight of possible by mounting the arms in ball bearings 12. The withdrawing movement is effected by the arms 10 and carrier 7 swinging outwards until arrested by a stop 13. With this arrangement the withdrawing movement is horizontal and the weight of the drill has no effect except that resulting from its frictional effect. The withdrawing force exerted by the weight can thus be adjusted as required without reference to the weight of the drill; and would as a rule be very much smaller than said weight.

Afurther important feature of the invention is that a portion only of the body is heated to the temperature at which complete or substantial loss of magnetism occurs; whilst however the effective magnetic field extends or may be extended to the unheated or less heated part of the body where little or no change of magnetic property occurs.

Thus in the example shown, the end portion 6 only of the drill is required to be heated to the treatment temperature, said end being positioned for that purpose in the hot part of the mufile. Current is supplied to the magnet 9 through a current controller 14 by adjustment of which the stren th of the magnet may be varied. The e ective ma etio field may for instance extend as indicated by the lines of force 15 to include the end portion 6 of the drill which is to be treated, and back from the end to include the portion'fi When therefore the end portion reaches, say, the hardening temperature and so becomes non-magnetic, the magnetic attraction is still exerted on the further portion 6". If this remaining magnetism is just overcome by the withdrawing force of the weight 8, the article will be withdrawn fromthe furnace when its end 6 has just reached or slightly exceeded the temperature at which the-steel becomes non-magnetic. In the case of heating high carbon steel to be hardened. it would be the correct temperature at which to withdraw the steel for quenching, the non-magnetic temperature and that of decalescence being the same.

In the case of alloy and low carbon steels however the decalescence temperature is sub stantially above that at which the steel becomes non-magnetic. Accordingly for such steels the current strength is increased to cause the eifective magnetic field to extend further back from the point of the drill, say to the oint 6. Before this increased magnetic orce is over-balanced by the withdrawing Weight, the drill will remain in the furnace long enough for the end 6 to attain a temperature substantially over that of nonmagnetism and until the heat extends rearwardly for a further length of the steel to become non-magnetic.

On the other hand it will be evident that by decreasing the strength of the magnet the temperature of withdrawal may be lowered to any temperature at which some loss of magnetism occurs, for instance for tempering or annealing. It will be seen that the automatic Withdrawal of a locally heated article may be effected at any desired temperature (of the most highly heated part of the body) Within a range varying from that at which magnetism begins to disappear to temperatures substantially above that at which magnetism totally disappears.

The effective retaining or withdrawing force being the difference of the magnetic attraction and the force exerted by the weight, it will be evident that either the ma etic strength or the weight may be varied. The most convenient method however, is to vary the magnet current strength and to keep the weight constant except for such slight adjustment as may be necessary to compensate for frictional variation due to considerable difierences in the weight of the articles treated. It will be evident that in treating large batches of articles of the same material which do not vary very much in weight, and for an identical purpose such as hardening, no adjustment of either the magnet strength orof the weight is necessary.

If an article is required to be heated throughout to a temperature above that at which it totally loses magnetism, it is made a part of a ferrous body which as a whole is on y partly heated.

In Fig. IV 16 indicates a small article of alloy steel which is to be hardened throughout. It is mounted upon an elongated holder 17 of iron or steel which exposes the article for heating and which itself rovides a substantial body of metal extending away from the article and capable of being heated and acted upon by the magnet. The attraction of the magnet on the holder retains the as sembly in the "furnace after the article has become non-magnetic and until the holder itself loses sufiicient magnetism to allow the withdrawing force to act. Moreover the article 16 may be of non-magnetic material, in which case the withdrawal would be determined solely by the change of magnetism due to the heating of the holder.

I claim:

1. The method of heating a magnetic body, which consists in mounting the body for movement to position it in a heating zone or withdraw it therefrom and so that the weight of the body has no material effect on its movement, subjecting it whilst in the heating zone to magnetic attraction tending to retain it in said zone, simultaneously applying to the body a retractive force, and relatively adjusting the retractive force and the magnetic force to cause the body to be retracted at a desired temperature.

' 2. The method of heating a magnetic body, which consists in mounting the body for movement to position it in a heating zone or withdraw it therefrom and so that the weight of the body has no material effect on its movement, subjecting it Whilst in the heating zone to magnetic attraction tending to retain it in said zone, simultaneously applying to the body a retractive force, and a justing the magnetic force to cause the retractive force to exceed the magnetic force upon a desired temperature being reached.

3. The method of heating a magnetic body which consists in supporting the body for movement, exposing only a portion of it to a heating influence, forming a magnetic field which effectively embraces said portion or" the body and adjacent portions, simultaneously applying to the body a retractive force which becomes efiective to withdraw the body from the heating influence upon the ma netic attraction falling due to heating of the body, and relatively adjusting the strength of the magnetic field and the retractive force to cause the latter to become efl'ecive when the heated portion of the body reaches a given temperature.

4'. The method of heating a magnetic body which consists in supporting the body for movement, exposing only a portion of it to a heating influence, forming a magnetic field which effectively embraces said portion of the body and adjacent portions, simultaneously applying to the body a retractive force which becomes effective to withdraw the body from the heating influence upon the magnetic attraction falling due to heating of the body and adjusting the magnetic field to cause the retractive force to become effective to withdraw the body from the heating influence upon its heated portion reaching, a given temperature.

5. A furnace for heat treatment of bodies comprising-a heating chamber, means movably supporting the body to, position it in and out of said heating chamber, a magnet exertbody to withdraw it from the heating chamber and means for relatively adjusting both the magnetic force and the withdrawing force.

6. A furnace for'heat treatment of bodies comprising a heating chamber, means movably supporting the body to position it in and out of said heating chamber, a magnet exerting magnetic attraction on the body 'in the heatin chamber, means exerting force on the b0 y to withdraw it from the heat- 15 ing chamber, and means for varying the magnetic field about the body in the heating chamber.

7. A furnace for heat treatment of bodies comprising a heating chamber, means movably supporting the bod to position it in and out of said heating 0 amber, an e1ectromagnet exerting magnetic attraction on the body in the heating chamber, means ex: erting force on the body to withdraw it from the heating chamber, and means for varying the current strength of the magnet.

In testimony whereof I aflix my signature.

DAVID STANISLAUS ODONOVAN. 

